The final two wells of a five-well, coiled-tubing drilling (CTD) campaign in shallow reserves of the Kansas Niobrara formation in the United States were successfully drilled using drilling mud in the vertical bore and air in the horizontal lateral, according to AnTech Ltd.

All five wells were drilled on the Colorado-Kansas border. The build sections of the final two horizontal wells were drilled with mud using an 8-1/2-in. bit. The horizontal sections were drilled with an air mist using a 6-1/4-in. bit. Air was used for these wells because the formations were highly fractured and were unable to hold the pressure of a liquid column.

The first horizontal well was drilled to 1,090 ft. true vertical depth (TVD) with over 1,450-ft lateral displacement. The team then carried out the second operation, another horizontal well drilled to 1,096 ft TVD with a lateral displacement of 1,103 ft.

Drilling of the final two wells, which were horizontal, demonstrated that AnTech’s POLARIS™ CTD bottomhole assembly (BHA) performs reliably when drilling horizontally.

As in the three previous directionally drilling operations, the 5-inch Polaris was easy to steer, reconfirming the effectiveness of the solid state gyro system and its overall ability to drill directional and horizontal wells, according to the company.

AnTech learned a lot about the system while drilling the two wells. Paul McCutchion, AnTech marketing manager, told Hart Energy E&P Online, “The main areas where lessons were learned were operational, and procedures have been changed accordingly, including allowing for the twist in the coil when kicking off, improving the choice of tool configurations (motor bend, etc.) for the different drilling requirements, and changing rig-up equipment and procedures to improve the process and increase efficiency.”

He explained that “while drilling with the air mist, we were able to demonstrate our underbalanced drilling capabilities, while also testing the reliability of the tool.

“When drilling with air, the tool is subject to harsh vibrations. Indeed, with our BHA, we were able to measure this, and we experienced vibration spikes of over 250 g (gravitational acceleration). This vibrational data can be used to fine tune the design of the tool and also help to optimize future drilling processes and operations,” he added.

The AnTech team worked in conjunction with a CTD specialist using one of the latter’s fleet of hybrid land rigs. By using a hybrid drilling rig, drilling time is often reduced. The same company had demonstrated on previous vertical wells that it could reduce the drilling time from seven to two days, compared to a conventional jointed-pipe rig.

“For years, the industry has been looking for an effective solution that combines the well- proven speed and efficiency of CTD with a directional capability that can not only drill hole sizes up to 8-1/2-in. and drill underbalanced to avoid over pressurizing the reservoir, but can orient while remaining in the casing,” said Toni Miszewski, managing director, AnTech.

“The fact that we were able to achieve this during the Niobrara drilling program demonstrates that the new Polaris provides a field-proven solution in the form of a gyro-steered BHA for use on coiled tubing,” he added.

“We believe that the new Polaris tool system will open up CTD to a new market, making the drilling of larger hole sizes economical for CTD,” McCutchion noted.

“For us, the main aim moving forward is to adapt the technology to suit this market as it evolves. The techniques used need to become as efficient as possible. Therefore, technology improvements to the operational procedures will be a major part of this.

“For the immediate future, the aim is to further our experience with these tools in commercial operations. However, there are a number of future developments in the pipeline to develop the technology both in terms of expanding the BHA capabilities and to improve operational planning with developments in well modeling and analysis,” he continued.

Looking ahead, AnTech is confident that the POLARIS system holds the key to unlocking reserves in mature oilfields and in shallow reserves previously thought to be commercially unviable, especially in the U.S.

“There is considerable interest from the industry in many areas around the world,” McCutchion said. “We are continually receiving new inquiries and interest from service companies and operators alike in North America, China and the Middle East among others. Potential markets include shale plays, coal-seam operations and re-entry projects.”

The success of the final phase of this drilling program follows on the heels of the deviated and S-curve wells previously drilled in late 2011, stated the company.

Overall, the program showed that the Polaris is capable of directional and horizontal drilling of wells with hole sizes ranging from 6.25-in. to 8.5-in., using drilling mud and air, while demonstrating AnTech’s AcrobatTM gyro system.

This is the first time that a solid-state gyro has been used for directional measurement while drilling, providing reliable data at all inclinations (vertical, horizontal and during the build section), allowing orientation to be carried out accurately, even while in the casing.

Precise well plans can be followed and well paths can be optimized by kicking off early (with the gyro still within the casing) and reducing build rates, making it easier to run casing without losing valuable depth, according to the company.

Contact the author, Scott Weeden, at sweeden@hartenergy.com.

Comments